<template>
    <!-- 商品分类导航 -->
     <div class="type-nav">
            <div class="container">
                  <!-- 事件委托 -->
                <div @mouseleave="leaveIndex" @mouseenter="enterShow"> 
                    <h2 class="all">全部商品分类</h2>
                    <div class="sort" v-show="show">
                        <div class="all-sort-list2" @click="goSearch">
                            <!-- 一级分类 --> 
                            <div class="item" v-for="(c1,index) in categoryList" :key="c1.categoryId" :class="{cur:currentIndex == index}">
                                <h3 @mouseenter="changeIndex(index)">
                                    <a  :data-categoryName="c1.categoryName" :data-category1Id="c1.categoryId">{{c1.categoryName}}</a>
                                </h3>
                                <!-- 二级、三级分类 -->
                                <div class="item-list clearfix" :style="{display:currentIndex == index?'block':'none'}">
                                    <div class="subitem" v-for="c2 in c1.categoryChild" :key="c2.categoryId"> 
                                        <dl class="fore">
                                            <dt>
                                                <a :data-categoryName="c2.categoryName" :data-category2Id="c2.categoryId">{{c2.categoryName}}</a>
                                            </dt>
                                            <dd>
                                                <em v-for="c3 in c2.categoryChild" :key="c3.categoryId">
                                                    <a :data-categoryName="c3.categoryName" :data-category3Id="c3.categoryId">{{ c3.categoryName}}</a>
                                                </em>
                                            </dd>
                                        </dl>
                                    </div>
                                </div>
                            </div>
                        </div>
                   </div>
                </div>
                <nav class="nav">
                    <a href="###">服装城</a>
                    <a href="###">美妆馆</a>
                    <a href="###">尚品汇超市</a>
                    <a href="###">全球购</a>
                    <a href="###">闪购</a>
                    <a href="###">团购</a>
                    <a href="###">有趣</a>
                    <a href="###">秒杀</a>
                </nav>
              
            </div>
    </div>
</template>
 
<script>
import { mapState } from 'vuex';
// import _ from 'lodash'; 引入lodash全部的功能函数
//按需引入
import throttle from 'lodash/throttle.js'
export default {
  name:'TypeNav',
  data(){
    return {
       //存储用户鼠标移上哪一个一级分类
       currentIndex:-1,
       show:true  
    }  
  },
  //组件挂载完毕：可以向服务器发送请求
  mounted(){
     //通过Vuex发请求，获取服务器数据，存储在Vuex中
    // this.$store.dispatch('categoryList');
    //当组件挂载完毕，让show属性变成false
    if(this.$route.path != "/home"){
        this.show = false;     
    }
  },
  computed:{
     ...mapState({  //TODO？？？
         categoryList:state=>state.home.categoryList   
      }), 
    // ...mapState('home',['categoryList']) ????
     
  },
  methods:{
    //  changeIndex(index){ //index:鼠标移上某一个一级分类的索引值
    //      this.currentIndex = index;  
    //  },
    //节流写法
     changeIndex:throttle(function(index){
        this.currentIndex = index;  
     },50),
     //当鼠标离开时，让商品分类进行隐藏
     leaveIndex(){
        this.currentIndex = -1; 
        if(this.$route.path != "/home"){
            this.show = false;     
        }
     },
     goSearch(event){
        //最好解决方案：编程式导航 + 事件委派
        //点击a标签的时候,才会进行路由的跳转  
        //问题一：如果确定点击的是a标签
        //给a标签加上自定义属性data-categoryName
        //获取当前触发这个事件的节点，带上data-categoryname属性一定是a标签
        let element = event.target;
        console.log(element.dataset); //获取节点的自定义属性和属性值 
        let {categoryname,category1id,category2id,category3id} =  element.dataset;
        if(categoryname){
            //区分一级、二级、三级分类的a标签(自定义属性：:data-category3Id="c3.categoryId")
            let location = {name:'Search'}  
            let query = {categoryName:categoryname} 
            if(category1id){
                query.category1Id = category1id;
            }else if(category2id){
                query.category2Id = category2id; 
            }else{
                query.category3Id = category3id;    
            }
            //如果路由跳转时，带有params参数，也需要传递
            if(this.$route.params){
                location.params = this.$route.params 
            }
            //组合参数
            location.query = query
            //进行路由跳转  
            this.$router.push(location)
        } 
     },
     //当鼠标移入时，让商品分类列表展示
     enterShow(){
       this.show = true;
     }  
  }
}
</script>

<style lang="less" scoped>
    .type-nav {
    border-bottom: 2px solid #e1251b;

    .container {
        width: 1200px;
        margin: 0 auto;
        display: flex;
        position: relative;

        .all {
            width: 210px;
            height: 45px;
            background-color: #e1251b;
            line-height: 45px;
            text-align: center;
            color: #fff;
            font-size: 14px;
            font-weight: bold;
        }

        .nav {
            a {
                height: 45px;
                margin: 0 22px;
                line-height: 45px;
                font-size: 16px;
                color: #333;
            }
        }

        .sort {
            position: absolute;
            left: 0;
            top: 45px;
            width: 210px;
            height: 461px;
            position: absolute;
            background: #fafafa;
            z-index: 999;

            .all-sort-list2 {
                .item {
                    h3 {
                        line-height: 30px;
                        font-size: 14px;
                        font-weight: 400;
                        overflow: hidden;
                        padding: 0 20px;
                        margin: 0;

                        a {
                            color: #333;
                        }
                    }

                    .item-list {
                        display: none;
                        position: absolute;
                        width: 734px;
                        min-height: 460px;
                        background: #f7f7f7;
                        left: 210px;
                        border: 1px solid #ddd;
                        top: 0;
                        z-index: 9999 !important;

                        .subitem {
                            float: left;
                            width: 650px;
                            padding: 0 4px 0 8px;

                            dl {
                                border-top: 1px solid #eee;
                                padding: 6px 0;
                                overflow: hidden;
                                zoom: 1;

                                &.fore {
                                    border-top: 0;
                                }

                                dt {
                                    float: left;
                                    width: 54px;
                                    line-height: 22px;
                                    text-align: right;
                                    padding: 3px 6px 0 0;
                                    font-weight: 700;
                                }

                                dd {
                                    float: left;
                                    width: 415px;
                                    padding: 3px 0 0;
                                    overflow: hidden;

                                    em {
                                        float: left;
                                        height: 14px;
                                        line-height: 14px;
                                        padding: 0 8px;
                                        margin-top: 5px;
                                        border-left: 1px solid #ccc;
                                    }
                                }
                            }
                        }
                    }

                    // &:hover {
                    //     .item-list {
                    //         display: block;
                    //     }
                    // }
                }
                .cur{
                   background-color: skyblue;  
                }
            }
        }
    }
}
</style>